The invention relates to an abrasive method for removing coatings, such as paint, decorative films, and overlays of plastic surfacing, especially plastic laminates. The invention furthermore relates to an apparatus for the practice of the method.
The term "plastic laminates," as used herein, refers to multilayer pieces of support materials, such as glass fiber, carbon fiber or plastic fiber fabrics which are cemented together with bonding agents (laminating resins) such as epoxy and melamine resins, thermoplastics, etc. Such laminates are used for technical purposes, especially in aircraft, motor vehicle and boat construction, but also for sporting equipment--skis, for example--and for furniture and the like. For example, the laminates consist of several layers of core film and a decorative film based on an amino plastic resin basis as the surface layer and, in some cases, a transparent or colored overlay pressed over the decorative film. The laminates are made by layering the resin-impregnated support materials.
A typical example of such laminates are helicopter rotor blades, in which the support materials are covered all the way into the outer area, with only a relatively thin coating of plastic. The cover layer in turn is covered with a coat or paint or decorative film. After a certain period of use, or also in the event of damage, the coating must be stripped from the helicopter rotor blades. Heretofore a manual method has primarily been used, i.e., using sanding blocks or abrasive sponges to rub off the surface manually until the coating is removed. Problems have arisen, due on the one hand to the heavy labor involved, and on the other hand to the health hazard constituted by the dust. Lastly, in military use problems have arisen due to the fact that the sometimes very sensitive parts are maliciously damaged and the damage can hardly be detected.
Attempts have therefore already been made to perform an abrasive treatment with abrasive particles fed in a known manner by means of a compressed air hose and a nozzle and driven against the surface. It has been found, however, that such an abrasive method is not easy to perform, and that the accompanying air does not accurately control the amount of the particles, so that erosion and damage to the support material in the laminate occur, because the surface is removed too rapidly.
The problem therefore arises of devising an abrasive method which will leave the very sensitive plastic laminates unharmed and will nevertheless permit the gentle removal of coatings of the kind described above, so that the disadvantages cited above will not be incurred. The method is furthermore to be easy to automate, so that it will not involve a great number of personnel.